Sources
| Therapeutic Dosages
| Therapeutic Uses
|
What Is the Scientific Evidence for Coenzyme Q
10
?
| Safety Issues
| Interactions You Should Know About
Coenzyme Q
10
(CoQ
10
), also known as ubiquinone, is a major part of the body's mechanism for producing energy. The name of this supplement comes from the word ubiquitous, which means "found everywhere." Indeed, CoQ
10
is found in every cell in the body. It plays a fundamental role in the mitochondria, the parts of the cell that produce energy from glucose and fatty acids.
Japanese scientists first reported therapeutic properties of CoQ
10
in the 1960s. Some evidence suggests that CoQ
10
might assist the heart during times of stress on the heart muscle, perhaps by helping it use energy more efficiently.
CoQ
10
's best-established use is for congestive heart failure, but the evidence that it works is not entirely consistent. Ongoing research suggests that it may also be useful for other types of heart problems, Parkinson's disease, and several additional illnesses. It is generally used in addition to, rather than instead of, standard therapies.
CoQ
10
supplementation might also be of value for counteracting side effects of certain prescription medications.
Sources
Every cell in your body needs CoQ
10
, but there is no dietary requirement as the body can manufacture CoQ
10
from scratch.
Therapeutic Dosages
The typical recommended dosage of CoQ
10
is 30 mg to 300 mg daily; higher daily intakes have been used in some studies.
CoQ
10
is fat soluble and may be better absorbed when taken in an oil-based soft gel form rather than in a dry form such as tablets and capsules.
1,81
Dividing the total daily dosage up into two or more separate doses may produce higher blood levels.
81
A finely ground up (“nanoparticular”) form of the supplement appears to be much better absorbed than standard CoQ
10
products.
86
Therapeutic Uses
Although not all studies have been positive, some evidence supports the use of CoQ
10
for treating
congestive heart failure
.
33-36,51-52,66,83
Keep in mind that CoQ
10
is taken
along with
conventional medications, not as a replacement for them.
Weaker evidence suggests that this supplement may be useful for
heart attack recovery
,
63,64,67,68cardiomyopathy
,
5-7hypertension
,
8-11,58diabetes
,
40,58
strengthening the heart prior to heart surgery,
69
and
migraine headaches
.
75
Although CoQ
10
has been widely advertised as effective for treating and
Parkinson's disease
, in fact, there is only minimal evidence that it works, and some evidence that it does not work.
57,65,86
CoQ
10
has shown the potential to prevent heart damage and other side effects caused by certain types of
cancer chemotherapy
.
59-61
This evidence is weak, however, and as yet it cannot be stated with any certainty that CoQ
10
is actually helpful.
70
CoQ
10
has shown some preliminary promise as an aid to the treatment of kidney failure.
49
Note:
People with severe illnesses, such as heart disease, cancer, or kidney failure, should not use CoQ
10
, or any supplement, except under physician supervision.
Highly preliminary studies suggest CoQ
10
might be helpful for
amyotrophic lateral sclerosis
.
13,14
CoQ
10
has been tried but not found effective for the treatment of Huntington's disease.
48
Certain medications may interfere with the body's production of CoQ
10
, or partially block its function. The best evidence regards cholesterol-lowering drugs in the statin family, such as lovastatin (Mevacor), simvastatin (Zocor), and pravastatin (Pravachol), along with the supplement
red yeast rice
(which contains naturally occurring statins). These medications impair CoQ
10
synthesis as an inevitable side effect of their mechanism of action.
22-25,89
Since these drugs are used to protect the heart, and since CoQ
10
deficiency could in theory impair heart function, it has been suggested that this side effect may work against the intended purpose of taking statins. Furthermore, one might naturally guess that some of the side effects of statins could be caused by this induced CoQ
10
deficiency. However, studies designed to determine whether the use of CoQ
10
supplements actually offers any benefit to people taking statins have returned inconsistent results at best.
76,77,87,88,90,91
For several other categories of drugs, the evidence that they interfere with CoQ
10
is provocative but even less reliable. These include
oral diabetes drugs
(especially glyburide, phenformin, and tolazamide),
beta-blockers
(specifically propranolol, metoprolol, and alprenolol), antipsychotic drugs in the
phenothiazine
family,
tricyclic antidepressants
,
methyldopa
,
hydrochlorothiazide
,
clonidine
, and
hydralazine
.
26-31
Again, while in theory CoQ
10
supplementation might be helpful for people using these medications, there is no direct evidence to support this hypothesis.
CoQ
10
has also been suggested as a
performance enhancer
for athletes. However, while one
double-blind
study of 25 highly trained cross-country skiers found some benefit,
15
most studies evaluating potential sports supplement uses of CoQ
10
have returned negative rather than positive results.
16-21,78
CoQ
10
is also sometimes claimed to be an effective treatment for
periodontal disease
. However, the studies on which this idea is based are too flawed to be taken as meaningful.
12
Even weaker evidence, far too weak to rely upon at all, hints that CoQ
10
might be useful in some cases of
tinnitus
(ringing in the ear).
One preliminary study of CoQ
10
for people undergoing treatment for
HIV
found conflicting results; the supplement appeared to improve general well-being, but it did not protect mitochondria (as the researchers had hoped it would) and actually seemed to worsen symptoms of nerve-related pain (peripheral neuropathy).
71
Preliminary evidence, far too weak to be relied upon at all, has been used to suggest that coenzyme Q10 might be helpful for
asthma
,
82
as well as reducing the side effects (specifically, cardiac toxicity) of the cancer chemotherapy drug
doxorubicin
.
84
CoQ
10
has additionally been proposed as a treatment for a wide variety of other conditions, including
angina
,
cancer
,
male infertility
, muscular dystrophy, and
obesity
, but there is, as yet, no evidence that it is effective.
There is also some evidence that CoQ
10
may reduce the risk of
pre-eclampsia
(high blood pressure during pregnancy) in women who are at risk for this condition.
92
What Is the Scientific Evidence for Coenzyme Q
10
?
Congestive Heart Failure
Most but not all studies tell us that CoQ
10
can be helpful for people with
congestive heart failure
(CHF). In this serious condition, the heart muscles become weakened, resulting in poor circulation and shortness of breath.
People with CHF have significantly lower levels of CoQ
10
in heart muscle cells than do healthy people.
32
This fact alone does not prove that the
supplements will help CHF; however, it prompted medical researchers to try using CoQ
10
as a treatment for heart failure.
The largest study was a 1-year,
double-blind, placebo-controlled
trial of 641 people with moderate to severe congestive heart failure.
33
Half were given 2 mg per kilogram body weight of CoQ
10
daily; the rest were given placebo. Standard therapy was continued in both groups. The participants treated with CoQ
10
experienced a significant reduction in the severity of their symptoms. No such improvement was seen in the placebo group. The people who took CoQ
10
also had significantly fewer hospitalizations for heart failure.
Similarly positive results were also seen in other double-blind studies involving a total of more than 270 participants.
34-35,53,83
One double-blind study found that in people with heart failure so severe they were waiting for a heart transplant, use of CoQ
10
improved subjective symptoms.
72
However, two very well-designed double-blind studies published in 1999 and 2000 enrolling a total of about 85 people with congestive heart failure failed to find any evidence of benefit.
36,54
The reason for this discrepancy is not clear.
Cardiomyopathy
Cardiomyopathy
is the general name given to conditions in which the heart muscle gradually becomes diseased. Several small studies suggest that CoQ
10
supplements are helpful for some forms of cardiomyopathy.
37-39
Hypertension
An 8-week, double-blind, placebo-controlled study of 59 men already taking medications for
high blood pressure
found that 120 mg daily of CoQ
10
reduced blood pressure by about 9% as compared to placebo.
40
A 12-week, double-blind, placebo-controlled study of 83 people with isolated systolic hypertension (a type of high blood pressure in which only the "top" number is high) found that use of CoQ
10
at a dose of 60 mg daily improved blood pressure measurements to a similar extent.
50
Similarly, in a 12-week, double-blind, placebo-controlled trial of 74 people with diabetes, use of CoQ
10
at a dose of 100 mg twice daily significantly reduced blood pressure as compared to placebo.
58
Antihypertensive effects were also seen in previous smaller trials, most of which were not double-blind.
41-43
CoQ
10
may also be beneficial in reducing the risk of high blood pressure during pregnancy (
pre-eclampsia
).
92
Two hundred and thirty-five pregnant women at risk for pre-eclampsia were randomized to receive CoQ
10
(200 mg daily) or placebo for 20 weeks until they delivered their babies. The women in the treatment group had fewer cases of pre-eclampsia compared to those who took the placebo.
Heart Attack Recovery
In a double-blind trial, 144 people who had recently experienced a
heart attack
were given either placebo or 120 mg of CoQ
10
daily for 1 year, along with conventional treatment.
63,73
The results showed that participants receiving CoQ
10
experienced significantly fewer heart-related problems, such as episodes of angina pectoris or arrhythmia, or recurrent heart attacks.
A double-blind study of 49 people who had suffered a full cardiac arrest requiring cardiopulmonary resuscitation (CPR) found that use of CoQ
10
along with mild hypothermia (chilling of the body) was more effective than mild hypothermia plus placebo.
74
Note:
Individuals recovering from a heart attack should not take any herbs or supplements except under the supervision of a physician.
Parkinson’s Disease
A study published in 2002 raised hopes that CoQ
10
might help slow the progression of Parkinson’s disease.
In this 16-month, double-blind, placebo-controlled trial, 80 people with Parkinson’s disease were given either CoQ
10
(at a dose of 300 mg, 600 mg, or 1,200 mg daily) or placebo.
57
Participants in this trial had early stages of the disease and did not yet need medication. The results appeared to suggest that CoQ
10
, especially at the highest dose, might have slowed disease progression. However, for a variety of statistical reasons, the results were in fact quite inconclusive.
A subsequent double-blind, placebo-controlled study of 28 people with Parkinson’s disease, which was well-controlled by medications, indicated that 360 mg of CoQ
10
daily could produce a mild improvement in some symptoms.
65
Based on these results, a more substantial study was undertaken, enrolling 131 people with Parkinson’s disease (again, well-controlled by medications).
86
This repeat trial used a specially finely ground up form of CoQ
10
that, though taken at a dose of only 300 mg daily, produced blood levels of the supplement equivalent to those produced by 1,200 mg daily of ordinary CoQ
10
. Unfortunately, it didn’t work. While benefits were seen in both the placebo and the CoQ
10
group, CoQ
10
failed to prove
more
effective than placebo.
Further trials will be necessary to confirm (or deny) these results.
Diabetes
In the 12-week, double-blind, placebo-controlled trial of 74 people with
diabetes
mentioned above, use of CoQ
10
at a dose of 100 mg twice daily significantly improved blood sugar control as compared to placebo.
58
Similar benefits were seen in the 8-week, double-blind, placebo-controlled study of 59 men also described above.
40
However, a third study failed to find any effect on blood sugar control.
62
Safety Issues
In general, CoQ
10
appears to be extremely safe. No significant side effects have been found, even in studies that lasted a year.
44,79
However, people with severe heart disease should not take CoQ
10
(or any other supplement) except under a doctor's supervision.
As noted above, two studies suggest that CoQ
10
might reduce blood sugar levels in people with diabetes.
45
While this could potentially be helpful for treatment of diabetes, it might present a risk as well; people with diabetes who are using CoQ
10
might inadvertently push their blood sugar levels dangerously low. However, another trial in people with diabetes found no effect on blood sugar control.
46,58
The bottom line: If you have diabetes, make sure to track your blood sugar closely if you start taking CoQ
10
(or, indeed, any herb or supplement).
CoQ
10
chemically resembles
vitamin K
. Since vitamin K counters the anticoagulant effects of
warfarin
(Coumadin), it has been suggested that CoQ
10
may have the same effect.
47,55
However, a small, double-blind study found no interaction between CoQ
10
and warfarin.
56
Nonetheless, in view of warfarin’s low margin of safety, prudence indicates physician supervision before combining CoQ
10
with warfarin.
CoQ
10
might also interact with reverse transcriptase inhibitors used for treatment of HIV (for example, lamivudine and zidovudine). These medications can cause damage to the mitochondria, the energy-producing subunits of cells, leading in turn to a variety of side effects, including lactic acidosis (a dangerous metabolic derangement), peripheral neuropathy (injury to nerves in the extremities), and lipodystrophy (cosmetically undesirable rearrangement of fat in the body). The supplement CoQ
10
has been tried for minimizing these side effects, but unexpected results occurred. In a double-blind, placebo-controlled study, use of CoQ10 improved general sense of well-being in people with HIV-infection using reverse transcriptase inhibitors; however, for reasons that are unclear, it actually worsened symptoms of peripheral neuropathy.
80
For this reason, people with HIV who have peripheral neuropathy symptoms should use CoQ
10
only with caution.
The maximum safe dosages of CoQ
10
for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been determined.
Interactions You Should Know About
-
You may need more CoQ
10
if you are taking:
-
You should not take CoQ
10
except on a physician's advice if you are taking:
-
CoQ
10
might improve general sense of well-being, but worsen peripheral neuropathy symptoms if you are taking: